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Publication Abstract

Owing to continuously increasing needs for water
and the limited available ground water in some areas
of Illinois, demand for water in the future will of
necessity be obtained in progressively larger
amounts from surface' water resources.

This bulletin provides data on water quality in
19 streams at 21 sampling locations and at 2 locations
on Crab Orchard Lake, the largest artificial
lake in Illinois. Over 1200 samples have been analysed
for 14 to 16 constituents in each. A tabulation
of the quality determinations for each of the streams
and for Crab Orchard Lake are included with temperature
and flow data in the Appendix.

The water samples were analysed for all the
usual mineral constituents, but not all constituents
were used to compare the quality of water in the
various streams for this bulletin. Probability charts
were prepared to include long-term average flow,
temperature, turbidity, hardness, alkalinity, total
dissolved minerals, and the ratio of alkalinity to
total dissolved minerals at the 23 sampling locations.
Only the above characteristics were treated
statistically in this bulletin because they are generally
considered the best criteria of suitability for
various uses.

No attempt has been made to convert the data
for the purpose of indicating the quality ranges that
might be expected from a reservoir. The quality of
stored water is less variable and depends upon the
length of time the reservoir has been in operation
as well as the amount or percentage of runoff stored.
An important section of this bulletin concerns a
post-mortem statistical analysis and discussion to
indicate the significance, and reliability of the
sampling program and data.